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Abstract:

The ranges of great camas (Camassia leichtlinii) and small camas (C. quamash) overlap extensively in the western United States. Previous systematic treatments of the genus are inconclusive, as a recent flora classifies C. leichtlinii as a subspecies of C. quamash.
We investigated species boundaries and putative hybrid zones at multiple sites in the Willamette Valley of Oregon and in allopatric populations ranging as far north as British Columbia. Genotypic inferences from allozyme electrophoresis of 218 individuals yielded 12 resolvable loci across
three buffer systems. Lower mean Nei's genetic identity (I) in interspecific pairwise comparisons (0.76) than in intraspecific comparisons (0.91 for C. quamash and 0.89 for C. leichtlinii) indicates that these taxa are readily distinguishable using allozymes. Furthermore,
four alleles uniquely characterize either C. leichtlinii or C. quamash and five additional alleles are common in one species but rare in the other. In different, sympatric populations, C. quamash and C. leichtlinii also varied in interspecific genetic identity (Nei's
I = 0.66–0.87), and in the additivity of allozyme patterns for plants identified as putative hybrids based on morphology. Principal Component Analysis (PCA), hybrid indices, and the relatively large interspecific Nei's I suggest that hybrid formation and introgression are
discontinuous, occurring extensively only at one site. For all populations, allozyme data support species-level distinction of C. quamash and C. leichtlinii.